1. Field of the Invention
The present invention relates to a heat exchanger apparatus which may be effectively employed, for example, for an oil cooler which effects heat exchange between lubricating oil and cooling water for an automotive internal combustion engine for the purpose of cooling the oil.
2. Description of the Prior Art
A conventional heat exchanger apparatus of the type described above has heretofore been arranged such that an oil cooler is mounted on the upper side of an engine block or a filter bracket, and an oil filter is integrally mounted on the oil cooler through a bolt disposed in the center of the oil cooler, thus constituting a cooling system in which the oil is cooled before being introduced to the side of the engine. A cooling system of this type has recently been devised in which the oil filter is constituted by two filter element layers in order to cope with the need to filter a large amount of carbon contained in the engine oil (particularly for diesel engines). For example, as disclosed in the specification of Japanese Utility Model Unexamined Publication No. 149980/1978, the oil filter is constituted by two filter element layers, that is, a first filter element which serves as an ordinary oil filter and a second filter element for absorbing carbon. However, since the second filter element is extremely dense, the resistance against the oil passing therethrough (the pressure loss of the oil) is increased by a large margin, which fact unfavorably leads to a substantial reduction in the hydraulic pressure of the oil introduced to the engine. In order to avoid such a pressure reduction, an arrangement is employed in which directly introduced into an oil pan portion (an oil reservoir portion) in such a manner that a pressure difference is produced between the upstream and downstream sides of the second filter element, thereby allowing the oil to smoothly pass through the second filter element and thus to be filtered.
However, this arrangement disadvantageously prevents the above-described oil filter from being integrated with an oil cooler, since piping for introducing the oil into the oil pan portion is interposed between the oil filter and the oil cooler.